1. Field of the Invention
The present invention relates to a water pump for circulating the cooling water of an internal combustion engine. In particular, the present invention relates to a water pump for circulating the cooling water of an internal combustion engine which includes a water passage for connecting a water pump which is connected to one end of and driven by a cam shaft for a valve system arranged in a cylinder head to a cooling water passage in a cylinder block. With this arrangement, manufacturing costs can be reduced.
The present invention also relates to a mounting structure of a camshaft in an overhead valve (OHV) type internal combustion engine.
2. Description of Related Art
A conventional water pump for circulating cooling water of an internal combustion engine is known from Japanese Patent Publication No. 2,782,548, wherein the water pump is mounted on a cylinder head body and a water passage communicating with a delivery port of the water pump is formed in a cylinder head. Furthermore, the water passage communicates with a cooling water passage (water jacket) in a cylinder block to introduce cooling water into the cooling water passage.
In addition, a conventional water pump for circulating the cooling water of an internal combustion engine is known, wherein instead of foaming the water passage communicating with the delivery port of the water pump in the cylinder head, a hose communicating with the cooling water passage in the cylinder block is used to introduce cooling water into the cooling water passage.
However, in the conventional water pump for circulating the cooling water of an internal conventional engine, the water passage needs to be formed in a cylinder head so as to make the delivery plot of the water pump communicate with the cooling water passage in the cylinder block. In the case where a hose is used instead of the water passage, the procedure of connecting the hose is troublesome. This results in an increase in the number of foaming processes and the number of assembling processes in both cases.
Conventionally, in an overhead valve type internal combustion engine, push rods having a long size are interposed between a camshaft which is close to a crank shaft and rocker arms for driving valves in order to transmit rotation of the crank shaft to open and close the valves disposed at an upper portion of a cylinder.
However, the push rods are not suitable for high speed rotation because of is heavy initial weights.
There is an example where the camshaft is separated away from the crank shaft so as to a-range the cam shaft in a central portion of a cylinder block (Japanese Unexamined Patent Publication No. Sho 63-125139).
The overhead valve type internal combustion engine 01 of the example described above is illustrated in FIG. 8 of the present invention. A camshaft 015 is installed in the central portion of a cylinder block 03 interposed between a crank case 02 and a cylinder head 04. Furthermore, a cam chain 018 is suspended between a cam sprocket 017 of the camshaft 015 and a timing sprocket 016 of a crank shaft 08.
Push rods 024 brought into contact, at their lower ends, with cam followers 020 which rock by coming into contact with cam surfaces of the camshaft are extended upward, penetrate the cylinder head 04, and reach a cylinder head cover 05, whereby upper ends of the push rods rock the rocker arms.
Accordingly, when reciprocating motion of a piston 06 rotates the crank shaft 08 via a connecting rod 07, the camshaft 015 within the cylinder block 03 is rotated via the cam chain 018 and the cam followers 020 are rocked. The rocking motion of the cam followers 020 moves the push rods 024 up and down, and opens and closes the valves at prescribed timings via the rocker arms.
In the example stated above, the cam shaft 015 is located within the cylinder block 03 so as to come closer to the rocker arms disposed on the upper side than in the case of the general overhead valve type internal combustion engine where the camshaft is located within the crank case, to thereby shorten the lengths of the push rods 024.
Therefore, the inertial weights of the push rods 024 are smaller than those of the general type engine, so that the mounting structure for the camshaft illustrated in the example is applicable to a certain degree of high speed rotation.
However, the push rods 024 still have a long size, since the push rods 024 penetrate the cylindrical head 04 and lower ends thereof reach the vicinities of the central portions of the cylinder block 03. Therefore, the inertial weights of this type of the push rods 024 remarkably influence on high speed rotation.
Furthermore, since the camshaft 015 is disposed at the central portion within the cylinder block 03, in the case where the cams are required to be replaced due to maintenance or the like, the cylinder block 03 must be removed on account of the necessity of removing the cam chain, and therefore it is not easy to replace the cams.